As has been mentioned previously here (and in many, many other places), Novak Djokovic won the French Open. That completes the career Slam for him (and the consecutive Slam), making him the first player since a lot of different people to do a lot of different things. (Among others, he's the first since Rafael Nadal to complete the career Slam, the first since Jim Courier to win the Australian and French in the same year, and the first since Rod Laver to hold all four Slams at once.)
So let's check and see what Grand Slam Scores now think of his career as a whole. (And, you know, everyone else. But mostly Djokovic, come on.)
This will be using the odds-based version of the system. (The results from the ranking-based version are currently more similar to the odds-based version than they've ever been.)
1. Roger Federer 26.72
2. Novak Djokovic 19.55
3. Rafael Nadal 19.00
Yes, that is the top three players of the last decade showing up in the top three places on the all-time list.
There are any number of arguments that can be made in terms of all-time rankings of tennis players, and I'm not going to pretend to address all of them right now. I will, however, say that Djokovic, Nadal, and Federer also rank 2 through 4 in Slam Score earned per Slam played, trailing only Bjorn Borg (who quit the sport before undergoing any kind of age-based decline), so their ranking is not simply a matter of being able to conveniently travel to more Slams (many of the top players of the past often skipped the Australian Open, for instance).
Why does Djokovic rank ahead of Nadal (and Pete Sampras, who's in fourth at 18.66)? After all, Nadal and Sampras both have 14 titles to Novak's 12, and if conventional accounting is to be believed, that should still give them an edge.
It does - just not enough of one to make up for Novak's other advantages. Djokovic has made 20 Slam finals, the same number as Nadal and two more than Sampras. In fact, in the odds-based formulation, Djokovic and Sampras get the same score from their final results: Djokovic has 12 wins (12 points) and 8 losses (4 points), to Sampras's 14 wins (14) and 4 losses (2).
Nadal still leads when accounting for titles and finals, however, so it falls to the previous round to give Novak his edge. Djokovic has reached 30 Grand Slam semifinals, far more than Nadal and Sampras's 23. (He trails Jimmy Connors, who had 31, and Federer, with 39.) Accounting for the extra semis in Novak's pocket puts him ahead of both of the alternatives for the #2 spot (Djokovic has 18.5 points through the semis, Nadal 17.75, Sampras 17.25), and there's not much movement from there. (All three players have lost exactly 6 quarterfinals. Nadal and Sampras have both suffered more defeats before that round - 10 for Novak, 16 for Rafa, and 23 for Sampras - but the extra early appearances don't make up much ground in their favor.)
Here's that information again in general list form. Note that the players are selected for the list based on Open Era performance, but pre-Open Era numbers are counted for the players who have them. (This works out nicely for Roy Emerson, but not so much for Don Budge.)
Slam titles won:
Slam finals reached:
Slam semis reached:
Slam quarters reached:
Note that Djokovic is in the top 4 in each of those lists - and apart from Federer, the identities of the players ahead of him often change. As such, if you use just those criteria, it is at least not easy to argue definitively against ranking Djokovic at #2.
And he's still going. He's the #1 player in the world, has won the last four Slams, has reached finals in 10 of the last 12, semis in 23 of 24, and 28 quarterfinals in a row. He's at an age where many great players before him (including Federer and Nadal) have slowed down - but if he's slowing down in any significant way, the evidence has yet to show up on the court.
It would take an awful lot for Djokovic to threaten Federer's spot at the top of the list, not least because Roger is still playing and playing well. But he has a great shot of at least climbing enough that he's closer to #1 than to #3.
Moving on down the list...
16. Boris Becker 11.39
17. Andy Murray 9.73
18. Guillermo Vilas 8.76
Murray is now solidly ensconced in no-man's land on the list, the conveniently large gap between the very good and the historically great. Everyone ahead of him has won at least six Slam titles.
Murray has won only two Slams - but he now ranks fifth (and counting) in most value accrued in Slams he hasn't won, trailing only Federer, Lendl, Connors, and Agassi. He's the same age as Djokovic and not quite as good, so the same caveats and a few more apply to his future performance - but he's likely to end up as the most underrated player ever, just because he chose a terrible time to be merely great rather than titanic.
30. Marat Safin 4.88
31. Stan Wawrinka 4.83
32. Yevgeny Kafelnikov 4.76
33. Pat Rafter 4.48
34. David Ferrer 4.30
35. Vitas Gerulaitis 4.28
It looks as though Stan is increasingly likely to be remembered as the fifth-best player of the Big Four generation. On one level, this is not entirely fair; his overall accomplishments don't necessarily stack up well against Ferrer's (he has 420 career wins to Ferrer's 679, and 14 titles to Ferrer's 26; both peaked at #3 in the rankings, but Ferrer has spent much more time in the top 10. Yes, Ferrer is older, but not by enough to explain away all of that difference). But on the other hand, Stan has the two Slam titles, and won them both the hard way - going through Djokovic and Nadal in one, and Federer and Djokovic in the other. Ferrer has had his chances to do that, and never pulled it off; even his lone final appearance came without meeting a member of the Big Four to that point in the tournament, and he was summarily dismissed in straight sets.
37. Gustavo Kuerten 4.13
38. Juan Carlos Ferrero 4.12
39. Tomas Berdych 3.92
40. Roscoe Tanner 3.83
44. Todd Martin 3.52
45. Jo Wilfried Tsonga 3.39
46. Sergi Bruguera 3.38
This section of the rankings contains two types of flawed players: guys who were great at one of the Slams but none of the others (Kuerten and Bruguera won five combined titles at Roland Garros, but never made much headway at the other three Slams), and guys who were good everywhere but never quite good enough (Berdych, Martin, and Tsonga are currently 2-3-4 on the Never Won a Slam list, and the two active players don't seem likely to depart that list at this point).
55. Marin Cilic 2.87
63. Juan Martin del Potro 2.60
108. Kei Nishikori 1.64
128. Milos Raonic 1.38
Those are the "young" players, with the word in quotes because Raonic, the youngest of the group, is already 25. They are, however, the only four players younger than Djokovic to rank among the top 200 in Slam Score (with the extra caveat that the lower you go on the list, the more likely it is that there are players missing from the database who could be included. Which doesn't make the current set of youngsters look any better.)
So if you're looking for an extra reason for optimism with regard to Djokovic and Murray continuing to move up the historical charts, that's probably it: there's still nobody who's ready to replace them at the top of the game.
Or at least, not as far as we can tell right now. But Wimbledon is coming, so we'll see...